Method of generating worm gearing



March 1930. s. l. `GONE` v I 157515540 METHOD oF' GENERATING woRM GEARING Filed Jun/e 27, 1925 2 sheets-sheet 2 Patented Mar. 25, 1930 entre srarss serena ori-fies SAMUEL I. GONE, OF PORTSMOUTH, VIRGINIA, ASSIGNOR TO GONE GEARING COPOR-A- TION, OF NORFOLK, VIRGINIA, A CORPORATION OF VIRGINIA METHOD OF GENERATING "WORM` GEARING Application filed .Tune 27, 1925.

it is anobject of the present invention to form the members of a system ofworm gearing with surfaces that can be easily cut, or so that bothfmembers of ,the system will be generated to a high degree of precision. An-

le other object of the invention is to generate worm gearing in which the flanks of the worm Wheel teeth have a twisted or warped surface correctly generated and disposed at an acute angle to each other and at acute angles to corresponding axial planes intersecting the teeth.

Another object of the invention is to provide a worm generated :for proper intermeshing relation With the above described worm wheel which will give a long and continuous contact, the contact between thevdriving surfaces of the thread of the worm and the driven surfaces of the meshed teeth of the worm wheel being such that the surface of the entering convolution oi the worm thread wipes 'a considerable portion ot the surface of the worm wheel tooth at that end of the worm, and diminishes gradually on consecutive convolutions of the worm thread until the leaving convolution of the worm thread Wipes a portion of the worm wheel tooth at that end of the worm. f

Still another object of the invention is to' provide a system of gearing permitting generating a worm either by using a cutting tool or tools mounted on a revolving table and so positioned ias they can be moved into the Work and along a line corresponding to the sides of the teeth of the worm wheel. axis of the revolving table on which are mounted the cutting tools for generating .the worm, and the axis of the cutter-bar for generating the gear wheel remain constant, and correspond to the working center distances, respectively, of the completed worm and wheel. The revolving table and Worm blank are geared together to travel in the designed ratio. The method of generating the worm preferably comprises mounting a number of- 0 tools on the revolving table corresponding to Serial No. 40,115.

the usual mid-plane of the worm wheel, with a means of lengthening or shortening the distances from the center of the revolving ta ble to the ends of the tools; and by this means the designed center distances can be maintained, and by 'starting with the tools set against the face of the worm blank and gradually lengthening the tools, they will iecd into the Work and generate a thread on the worm 0.4:' the correct angle, pitch and twist.

A further object of my invention is to provide a system of gearing permitting generating a worm Wheel either byvusing a tool or tools, so that their cutting edges are in a position corresponding tofpthat assumed by the sides of thread on the worm, and placed in such a position as to generate the angle, pitch and twist on the teeth to fit the above-dcscribed worm.

The method of generating the worm wheel is to mount the wheel blank on the revolving tablewith a revolving cutter-bar in the same positions formerly occupied respectively by the cutters and worm for generating the worm7 or, in other words, to reverse themeth# 0d oI'` generating the worm.` On the bar that replaces the worm, a tool or tools are so mounted thatthe lines of their cutting edges when projected intersect the center line of, the bar, and are placed in such a position that the cutting edges will generate the correct angle, pitch and twist on the teeth to it the angle, pitch and twist that are generated onthe worm. The centerlineof the cutter-bar and the axis of the wheel blank are set to correspond to the centers of the worm and wheel respectively. A means is provided for extending or shortening the length of the cut- The\ters in relation to the lcenter of the cutterbar. v

In starting to generate the teeth on the Worm wheel, the cutters are set to the short est required radius, and as the workprogresses the radius is lengthened-until the maximum length desiredr is reached. The cuttingedge of the cutter is always set at 90 degrees tthe centerline of the bar and`moves out from the center in a straight line. vIt can be seen that passing through the wheel it must cut a straight line radiating from the centerline of 1 the bar, and will 'generate an angle on the tooth' of the wheel. This angle depend on the position of the cutter in relation to a l ne drawn at 90 degrees from the centerline of the cutter barand intersecting the center of the wheel. This distance is equal to the radius of a circle co-axial with the axis of the wheel, said circle being definitely fixed by the angles 0f the teethbn the gear wheel, and ina manner hereinafter described. It can be readily seen that, as the cutters revolve through the wheel while the tooth that is being cut on the wheel is advancing in rotation, it follows Ithat the cutters must generate the proper twist to the teeth.

It will be notedthat the cutters that cut the corresponding sides of vboth the worm thread and theewheel `teeth be mounted for rotation at the same time, their edges or lilies of action in traversing their paths may be/brought coincident with each other in the axial section or mid-plane and at a predetermined distance from a line drawn at 90 degrees from the center line of the worm or :ut-ter bar and intersecting the axis of the revolving table and if the distances between the `axis of the revolving table andthe center line'of the worm or cuttcr-barremains constant the generated angle and pitch mustfbe the same inthe mid-plane `for both theworm and the wheel, the generated twist for bothx varying only the minimum thus giving the maximum bearing surface that it is possible to obtain. e

One of the advantages of my invention is that when the angle'of the gear wheel tooth has been selected, by utilizing my invention both the worm and the worm wheel can be definitely generated to the same pitch, and therefore when one convolutionof the thread of the worm is in contact with a tooth ofthe worm wheel, every convolt n of the worm thread will be in contact with its mating tooth of the wheel. For this reason the worm and wheel cannot wear out of pitchfwith each other, nomatter how much the gearing wears or how much backlash occurs. They will always be in pitch and every thread'convolution on the worm will be in bearing wit 1 a tooth on the wheel until the gears are worn out. 5

Vth theseand other objects in view, .my invention comprises the generating of the worm and worm wheel, whih are set forth in the following specifications, and illustrated l in the accompanying drawings. 4In the accompanying drawings annexed hereto, I have shown my invention embodied in one form of worm gearing having a. .single threaded worm, but it can be made with multiple threads. It will be understood that the invention can be otherwise vembodied and that the drawing is not to be construed as defining orlimiting 'the scope of the inven- I v tion, the claims appended to this specification being relied upon for this purpose.

Fig. 1 shows a view partly in `section of a worm and a worm wheel made in accordance with one of the modifications of the present invention Fig. 2 shows a methodof generating the flanks of the teeth ofjthe periphery .of the worm wheel; and i Fig. 3 shows a method of generating the Hanks of the thread on a worm made in accordance with the present finvention.

Briefly, my invention in its broadest @peet comprises an improved method of generating worms of the hourglass type and worm wheels having the correct angle, pitch, and twist, -thereby producing the maximum amount of contact between the flanks of the Worm thread and corresponding flanks of the teeth of the worm wheel throughoutthe length of the worm; the said maximum contact being secured` by locating the cutting edge of a Atool or tools at a certain predeter? mined position and-by maintaining a constant distance'between the centers of rotation and then feeding said tool or tools into the blanks in a certain designated manner, all of which is clearly set forth in this app ication.

In the usual or common method heretofore employed for forming the two members of a Hindley system, the worm is made first and then a hob of a form similarito that of the worm and whose cutting edges correspond with its thread. Lastly, the wheelfteeth/ are cut by bringing ,the rotating hob into the desired position with respect to the rotating wheel blank. The result of this operation is that inthe .development of the wheel teeth the hob convolutions do not work in harmony with each other, one convolution seating itself by removing material which is subsequently needed by another in seating itself.

To modify these' irregularities subsequent alterations to either the worm thread or wheel teeth, or both .are employed to affect an adjustment, the results being at the best faulty and indefinite.

By employing the methods described in the present invention, the worm and the wheel may each be completed and independently possessed `of the idealmating qualities.

In Fig. 1 a worm Wheel is'shown at l in mesh with a worm 7, both possessing the form resulting from the use of methods described in lthe present invention. The sectional portion shown is taken at the axial section or mid-plane in which plane each of th sides 1v1 of the thread 10 is coincident with one of the "sides 3 of the teeth 4, all being straight at this mid-plane section. The teeth l of the wheel 1 are equally spaced A and their sides 3 ar twisted as clearly shown.

:As shown in Fig. 2, these twisted surfaces,

forming the flanks 3 of the gear teeth, are f l an additional dotted view of a portion of the' Wheel and cutter isshown, thus presenting the action of both tools in the mid-plane.

The coaxial circle circumscribed about the axis 2 of the gear Wheel 1 is designated by thel numeral 14, and its diameter is fixed by the angle of the teeth on the gear Wheel when taken at the mid-plane. The length of the Worm with which the gear Wheel is to beintcrmeshed is preferably equal in length and never greater than the diameter of said circle. The'anks 3 of the teeth 4 are generated so 'that the line of projection of each flank in the mid-plane is tangent to this circle 14, and as shown in Fig. 2, the lines passing through the cutting edge of tools 5 are tangent to said circle. i

One of the cutting tools 5 on cutter bar 6, and the blank for the gear Wheel may be rotated simultaneously at a predetermined rate of speed relative to each other for generating one side of. each tooth when the cutting tool may be either reversed or another tool used for generating the opposite side of said teeth, as shown in Fig. 2. Further, instead of reversing the .cutting tool, it may remain the same and the gear blank may be reversed, if desired.. Adjustable means is provided for simultaneously feeding the cutting tool or tools into the blank as the Operation progresses. The lines 15 in Fig. 2 show the position of the tool or tools 5 at the beginning of the operation. y n

A Worm 7 adapted to engage-With Worm Wheel 1 is shown in Fig. 3. This is preferably generated integral on its shaft 8 and is adapted to be mounted to rotate about an axis 9 at right-angles to the axis 2 of the Worm Wheel 1. The Worm 7 is generated With a conti'nuous'thread 10 extending about the Worm 7 from end to end, The flanks or sides of thisthread 10, Which are shown at 11, are adapted to give contact With the flanks Bof the teeth 4 of theflvvorm Wheel 1, and these surfaces 11 are so generatedthat they Will intermesh properly with the gear Wheel 1 and give contact With the flanks 3 on said gear Wheel teeth throughout the are lof contactof Worm 7 With Worm Wheel 1. The surfaces 11 are not of true helicoidal form, but are peculiar warped surfaces, Which are generated in a novel manner, to give a conjugate form to their surfaces relative to the flanks 8 of the Worm Wheel 1.

The general shape of-Worm 7.is of the globoidal or hourglass Worm type, and the thread 10 is adapted to contact with the teeth 4 of gear Wheel 1 with a large surface contact on tooth 4 of gear 1 at the entering convolution of the thread 10 on the Worm 7 and gradually diminishing in surface contact until it reaches the leaving convolution of the threadof said Worm, at which place, it Wipes a portion of the flank surfaee of tooth 4. vEach of the teeth 4 on gear 1 within the arc subtended by the worm 7 is engaged `by a portion of the thread 10. I

The method' of generating the Worm 7 is clearly shown in Fig. 3. The tools 12 are mounted on a table 16 -to` revolve about the axis 2, and in the axial plane. of the Worin, and are so positioned that their Lsides coincide with a line that is tangent to a base circle 14,

concentric with axis 2, and are provided with U an adjustable means of moving them int/o Worm 7, the lines 17 indicating the positions I of tools 12 at the beginning of the operation.

The extreme length ofthe surface of Contact of the thread on Worm 7 With the surfaces of i teeth 4 on gear 1 is equal to the diameter of the base circle 14, and equals the distance between the positions where each of any pair of 'opposed flanks 11 of the thread 10 of Worm 7 forms a right angle to axis 9 of Worm 7.

This length of contact surface on Worm 7-is thus governed by the angle that it is desired to generate.

The cutting tools 12 for"generating the Worm are mounted on a table 16 to be revolved simultaneously with the rotation of the Worm blank on its shaft 8 at a predetermined ratio of speed., so that these cutting tools are fed into the Worm blank as the tablewiththe tools thereon is rotated, the tools and Worm blank being simultaneously rotated and positioned in accordance With my invention, the

l.proper thread Will be generated on the Worm.

AThe preferred means for carrying the invention into practice is disclosed in my application Serial No. 118,214.

For large speed. reductions, between the worm and Worm Wheel, l preferably utilize a single threaded Worm, and for a small speedv tool being radiated While rotated in a plane parallel with and spaced apart from a plane passing through theaxis ofthe Wheel blank and perpendicular to the axis of rotation of the cutting tool, the cutting edge lying at all times entirely Within a plane passing through the axis of rotation of said tool.

2. The methodof generating Worm Wheels adapted for use with worms of the Hindley tion of said,'tool, the distance between said screw type consisting in simultaneously rotataxes being maintained constant throughout ving n edge cutting tool and wheel blank the operation and the tool being advanced about two axes perpendicular to each other. into the worm wheel blank by increasing its to generate the faces of the worm wheel teeth, radial distance from the axis of rotation of the cutting edge of said cutting toolbeing the said'tool, and cutting-teeth upon said rotated and radiated in a plane parallel with wheel blank with a long helical twist and and spaced apart from a ;-plane passing with sides at a constant angle toeach other. through the center axis ofthe worm Wheel G. The method of generating a worm of blank and perpendicular to the axis of rotathe Hindley screw type including rotating a tion of the cutting tool, t.e cutting edge lygenerating tool and a worm blank simultaing at all times entirely within a plane passneouslyabout axes perpendicular to each ing through the axis of rotation of said tool. other, and at fixed center distances, and ef- 3. The method of generating worm wheels fectingrelative radiation for generating the of the character described, consisting in rotatthread on the worm. I ing and radiating an edge cutting tool and a 7. The method of generatinga worm of the worm wheel blank sin'iultaneously about two Hindley screw type consisting in rotating an axes perpendicular to each other to generate edge cutting tool and a worm blank simultathe faces of the worm wheel teeth, the plane neously about two laxes perpendicular to each of the cutting edge of the tool lbeing spaced other to generate the thread on the worm, apart from a plane passing through the axis maintaining a constant xed distance beot' the worm wheel blank a distance equal to tween said axes throughout the operation and the radius of the co-axial circle formed by gradually advancingthccutting tool into the `the projections of the faces of the worm Worm blank along the line of the side of the wheel teeth, and said plane of the cutting thread, as the Work progresses and 'cutting edge of said tool being parallel with the axis the worm thread, with a long helical twist of the Worm wheel blank and perpendicular and with sides at a Constant angle to each to the axis of rotation of said tool, the cutother.

ting edge lying at all times entirely within 8. The method of generating a Worm of the a plane passing through the axis of rotatioli Hindley screw type consisting in r tating of said tool. edge cutting tools and a worm blank simul- 4. The method of generating worm wheels taneously about two axes perpendicular to of the character described, consisting in roeach other` to generate the thread on the worm, tating and radiating an edge cuttingtool and maintaining a constant fixed distance between a worm wheel blank simultaneously about two said axes throughout the operation and gradaxes perpendicular to each other to generate ually advancing the cutting tools into the the faces of the worm wheel teeth, the plane worm blank along the lines of the sides ofthe of the cutting edge of the tool being spaced thread, as ,the work progresses, Vand cutting apart from a plane passing through the axisV the worm threads with a long helical twist ot' the worm wheel blank a distance equal to and with sides at a constant angle to each the radius of the co-axialcircle formed by other.

the projections of the faces of the worm wheel 9. The method of generating worms Aof the teeth and said plane of the cutting edge of character described,including simultaneously said tool being parallel with the axis of the rptating an edge cutting tool and worm blank Worm wheel blank and perpendicular to the about two axes perpendicular to each other axis of rotation of said tool and the distance while eecting relative radiation, the cutting between said axes being maintained constant 13001 being rotated in a plane parallel to the throughfmt the opelatolband Cutting ''eth' axis of the worm blank and the plane of the PQR Sad Whee1-b1ank Wlth 3f long hellal cutting edge of said tool being perpendicular twlst and .with sides at a constant angle to t the axis of rotation of 'Said Worm blank, each Othe'- the cutting edge lying at all times within a 5. The method of generating Worm wheels h h f t .f of the character described, consisting in no- ,ll'loslntlroug t e ams o ro anon o tating an edge cutting tool and a worm whee blank'simultaneously about two axes perpendicular to each other to generate the faces of the worm Wheel teeth, the plane of the cutting edge ofthe tool being spaced apart from a plane passing through the axis of the worm wheelblank a distance equal to the radius of the co-axial circle formed by the projections of the faces of the worm wheel teeth, and said planeof the cutting edge of the tool being parallel with `the axis of the worm wheel 4blank and perpendicular to the axis of rota- 10. The method of generating Worms of the e aracter described, consisting in rotating an edge cutting tool and a worm .blank simultaneously about two axes perpendicular' to each other to generate the surfaces of the threads of the Worm and effecting relative, radiation, the plane of the cutting edge of the tool being parallel with and spaced apart from a` plane passing through the axis of rotation of said toola distance equal to the raduis of the co-axial circle formed bythe the axis of rotation of said tool a distance projections of the faces of the worm wheel throughout the operationa fixed distance beteeth with which the said worm is to mesh, tween the axes of rotatlon, while radlally and said plane of the cutting edge of said feedmg the cutter tothe blank. `7

tool being perpendicular to the axis of rotation of the worm blank, the cutting edge lying at allitimes within a plane passing through the axis of rotation ofthe worm blank. v

11.l The method of generating worms of the character described, consisting in rotating an edge .cutting tool anda worm vblank simultaneously about two axes perpendicular to 'ea/ch other to generate the surfaces of the threads of the worm and effecting relative radiation, the plane of the cutting edge' of A the tool being parallel with and spaced apart from a plane passing through the axis of rotation of said tool a distance equalto the radius of the co-axial circle subtending the projections of the vfaces of the gear wheel teeth with which the said worm is to mesh and said plane of the cutting edge of saidtool being perpendicular to the vaxls of rotation of the taneously about two axes perpendicular to each other tofgenerat the surfaces of the threads of the worm, t e plane of the cutting edge of the tool being parallel with 'an spaced apart from a plane passing through of rotation of the worm blank and the dis-- tance' betweenA said axes being maintained constant throughout the operation and the tool being .advanced into the worm blankv by gradually increasing the distance between f.

cutting end of said tool and a plane perpen- "dicular to the plane of the cutting edge of said tool and passing-throughthe axis of rotation of same and cutting the worm thread "with a long helical twist and with sides at a constant angle to each other.

`55 V axes perpendicular to each other while effect- 13. 'In' the method of generating worm.

gearing,". which includes rotatinga cutting tool and a blank simultaneouslyabout two ing 'relative radiation, the, improvement which consists in maintaining throughout the cutting operation a fixed distance between v said axes.

14. In the production of gears of the Hindley type,the improvement which consists in generating the teeth by an end cutting operation "under conditions which will insure In testimony wher 

